Addition of eltrombopag to immunosuppressive therapy in patients with newly diagnosed aplastic anemia

Background: The immune-mediated destruction of hematopoietic stem cells is implicated in the pathophysiology of aplastic anemia (AA). Immunosuppressive therapy (IST) using antithymocyte globulin and cyclosporine is successful in this setting. Eltrombopag is active in patients with refractory AA, presumably by increasing the bone marrow progenitors. Methods: This phase 2 trial initially was designed to evaluate standard IST in newly diagnosed patients with severe AA and later was amended to add eltrombopag to simultaneously address immune destruction and stem cell depletion. The primary outcome was the overall response rate (ORR) at 3 months and 6 months. Results: A total of 38 patients were enrolled: 17 (45%) received IST alone and 21 (55%) received additional eltrombopag. The ORR was 74%. Patients receiving IST plus eltrombopag had a similar ORR (76% vs 71%; P =.72), complete remission rate (38% vs 29%; P =.73), and median time to response (84 days vs 57 days; P =.30) compared with those receiving IST alone. The 2-year overall survival rate in the IST group was 91% compared with 82% for those patients treated with IST plus eltrombopag (P =.82). No cumulative toxicities were noted after the addition of eltrombopag. Conclusions: The addition of eltrombopag to standard IST was well tolerated and resulted in similar responses.